It is generally known in the art to make tufted buffing pads by placing pile on the face surface of a backing pad with a tufting machine by starting near (one edge) of the backing pad and then sewing in a spiral or circular pattern to the other edge of the pad. Lateral movement of the backing pad in equal increments to place the piles in radially outwardly increasing spirals or concentric circles is accomplished by using the previous row of pile to push the pad outward, or by using a positive indexing means. The tufted buffing pads achieved by these prior known means are of constant density on the face surface thereof from its center to the outer periphery. A problem presented by such buffing pads when used in buffing or polishing applications is that high-wear pile areas of the buffing pad will wear down faster than the remaining low-wear pile areas resulting in a buffing pad that is worn out and no longer suitable for use, even though low-wear areas of the buffing pad are still in good condition. This is extremely wasteful of pile material and costly to the consumers.
There is a need, therefore, of an apparatus and method for solving the problems presented by the prior known tufted buffing pads. This was achieved by the method and apparatus of this invention for making improved tufted buffing pads of varied density on the face surface thereof, in which the pile density is low in low-wear areas and high in high-wear areas. Such buffing pads would be less costly to manufacture, requiring less pile material, would be more reliable in operation, and would have a longer life.
In U.S. Pat. No. 3,459,145, a self-programmed automatic embroidery system is disclosed which includes means to detect the edge of a workpiece or a heavy line drawn thereon, and to stitch around the edge of the workpiece or along the heavy line drawing exclusive of any external control. A read head is provided which is adapted to rotate around a needle axis. The output of the read head is converted into a pulse signal which is fed to an electrical step motor which drives a workpiece orientation feed guide means in a step-by-step manner either in a clockwise or counterclockwise direction, as required, to maintain the read head in its proper position to read the edge of the workpiece. Such a self-programmed automatic embroidery system is ineffective to solve the aforementioned problems presented by prior known tufted buffing pads of constant density on the face surface thereof.
In U.S. Pat. No. 3,367,294, a tufting machine pattern control arrangement is disclosed for use in making carpets or like fabrics wherein a pattern is formed in the work by selectively commanding the formation of pile loops of normal or reduced height respectively, by means such as a pattern drum. However, such a tufting machine pattern control arrangement would be wholly incapable of manufacturing a tufted buffing pad having low pile density in areas of low-wear, and a high density of pile in areas of high-wear.
In U.S. Pat. No. 3,385,244, an electronic control system for an automated sewing machine apparatus is disclosed. The control system and apparatus contemplates coupling electrical step motors to a work frame, such as a cloth frame, to supply a controlled intermittent step motion in both an X and a Y coordinate axis with respect to a sewing machine head each time the needle in the sewing machine head is out of the cloth during each stitching cycle. The motion of the cloth frame is controlled by means of a perforated tape reader, which feeds electrical signals into an X and Y logic circuit. A timing means is also coupled thereto for supplying enabling gates which allow command signals to be coupled to the step motors at selected times during which the needle is out of the cloth. The work frame is adapted to step in either the X or Y direction several times in response to information fed from the tape reader during each stitching cycle. Although the disclosed high-speed digital electronic controlled system is effective for operating one or more sewing machines in accordance with a prerecorded program, it would be ineffective for solving the problems presented by a prior known tufted buffing pad of constant density. The disclosed method and apparatus of U.S. Pat. No. 3,385,244 is incapable of making a tufted buffing pad of varying density in which the pile density is decreased in low-wear areas and increased in high-wear areas.
From a consideration of the prior art, it appears that no attempt was made to effectively solve the problems presented by tufted buffing pads of constant density across the face surface thereof. The problems, for example, involve tufted buffing pads that wear out quickly, that are wasteful of pile material, and have a low polishing efficiency. Therefore, an object of the present invention is to provide a tufted buffing pad of varied density on the face surface thereof from its center to its outer periphery in which the pile density is increased in the high-wear area and decreased in the low-wear area. This invention will enable a wool reduction of 5 percent to 15 percent and an increase in pile density in the high-wear area of 10 percent to 20 percent. The improved tufted buffing pad will have higher life expectancy and improved polishing efficiency.